This invention relates to an apparatus for feeding a fiber tuft mass (fiber batt), composed of, for example, cotton fibers, synthetic fibers or the like, to a fiber processing machine, such as a carding machine or a cleaner to prepare the fiber for spinning. The apparatus has a fiber advancing mechanism formed of a feed roll and a cooperating feed table followed by at least one opening device such as an opening roll. The fiber advancing mechanism also serves as a batt thickness sensor. For this purpose the feed table is formed of a plurality of individually movable feed table segments which undergo excursions as the throughgoing fiber batt changes in thickness. Each movable feed table segment is biased towards the feed roll by a spring arrangement and is connected, with the intermediary of the respective springs, with a rotatably supported biased common holding element which senses the sum of the displacements of the individual feed table segments.
In a known apparatus of the above-outlined type, generally referred to as pedal-type or piano key-type regulating device, a fiber batt feeding aggregate and a rapidly rotating opening roll are arranged in series. The batt feeding aggregate is formed of a feed roll with feed table and upstream thereof (as viewed in the direction of fiber feed) there is arranged a sensor device having a fiber batt advancing roll cooperating with a plurality of sensor fingers. Thus, the sensing and feeding of the fiber material to the opening roll are spatially separated. By means of the sensor fingers the sensor device mechanically detects thickness variations of the fiber batt at several locations along the width of the fiber batt. Each sensor finger is an angled, two-arm lever rotatably held in its mid portion. The free end zone of one lever arm forms the sensor member proper, while at the free end zone of the other lever arm a tension spring is attached. In this manner each sensor finger is movably mounted for displacement in response to thickness variations in the fiber batt and each sensor finger is individually biased by its tension spring in such a manner that the sensor fingers press the fiber material against the feed roll. All tension springs are attached with one of their ends to one lever arm of a rotatably supported common two-arm summing lever. The other arm of the summing lever is attached to a weight, whereby to each sensor finger a fiber material pressing force is imparted with the intermediary of the tension springs and the summing lever. With the other lever arm of the summing lever an inductive proximity switch is associated which transforms excursions into electric pulses. A delayed, path-dependent shift register ensures that the corresponding regulating pulse affects the rotary speed of the downstream connected feed roll of the feed roll/feed table assembly (feeding assembly) for the opening roll only when the respective sensed areas of the fiber batt arrive in the working zone of the fiber feeding assembly.
It is a disadvantage of the above-outlined prior art construction that it is structurally complex and it is complicated to assemble. A great number of individual structural elements are required, for example, a separate rotary bearing has to be provided in order to support individually each sensor finger. Such rotary bearings are complex, expensive and they must be aligned with high precision. It is a further disadvantage of the prior art arrangement that the sensor fingers are separately connected with the common summing lever. Thus, the tension springs are needed as separate force-transmitting elements between the lever arms of the sensor fingers and the spaced lever arm of the summing lever. The individual tension springs are attached (hooked) at their ends with a certain clearance and their elongation may lead to tolerances and deviations which jeopardizes accurate measurements during operation. Particularly the determination of the sum of the thickness deviations is imprecise because the excursion of each individual sensor finger is measured indirectly. Because of the possibility of deviations in the tension springs, a uniform clamping of the fiber material along its width is adversely affected as well.